Smoothing the Universe by Cosmological Contraction with Various Scalar Field Potentials

Abstract

The cosmological mechanisms for producing a smooth universe are disputed. This thesis details the motivation for, and explores the nature of, a smoothing mechanism in the form a slow contracting phase prior to the Big Bang. Cosmological smoothing is achieved by the introduction of a scalar field with equation of state w ≥ 3 (ε ≥ 3) rolling down a negative exponential potential. It is important to examine various extensions of this potential and their ability to achieve and maintain smoothing. Specifically, two extensions are examined: a purely negative potential with a minimum, and a potential which begins negative and becomes positive beyond the minimum. For the purely negative potential with a minimum, it is found that smoothing can be achieved and maintained with some deviation from the simple negative exponential. In the case of the potential with a positive region, it is found that smoothing is achieved after the same number of e-folds for a wide range of gradients in the positive exponential region. Moreover, it is shown that smoothing can be achieved if the scale factor w < 1 (ε < 3) for a brief period in the latter potential.